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Abstract

A method is described that can be used to reduce the amount of time and power required to perform displacement amplification procedures in direct access storage device (DASD) files that employ sensorless spindle motor systems, procedures which are sometimes necessary to overcome stiction forces during the spindle startup procedure. This method utilizes a means to determine the positional relationship of the rotor and stator of a sensorless spindle motor such that the most optimum motor drive current phases can be energized during the displacement amplification procedures.

Country

United States

Language

English (United States)

This text was extracted from an ASCII text file.

This is the abbreviated version, containing approximately
53% of the total text.

A method is
described that can be used to reduce the amount of
time and power required to perform displacement amplification
procedures in direct access storage device (DASD) files that employ
sensorless spindle motor systems, procedures which are sometimes
necessary to overcome stiction forces during the spindle startup
procedure. This method utilizes a means
to determine the positional
relationship of the rotor and stator of a sensorless spindle motor
such that the most optimum motor drive current phases can be
energized during the displacement amplification procedures.

A 3-phase
brushless DC spindle motor has six possible
combinations of motor drive current phases, one of which will produce
the maximum torque in the desired direction for a given spindle motor
rotor and stator positional relationship.
Previous brushless DC
motor designs utilized Hall sensors to determine the rotor position,
and hence the correct drive phases to apply during displacement
amplification could be easily determined.
Modern brushless DC motor
designs do not utilize Hall sensors to determine the rotor position,
instead, some form of back-EMF sensing is used to determine the rotor
position for commutation. However, if the rotor is not moving (or is
moving very slowly), then a measurable back-EMF does not exist.